1. Field of the Invention
The present invention relates to an image display apparatus.
2. Description of the Related Art
An image display apparatus called head-up display to be mounted on a moving body (object), such as an automobile, aircraft, and a ship, has been known. A head-up display is an image display apparatus for displaying various types of information related to operations of the moving body in a manner easily visible to the user. A head-up display includes an optical element called combiner, and projects and displays image light for displaying the information upon the combiner. The image light projected on the combiner presents display related to the information to the user in a manner such that the display can be visually observed as a virtual image farther than the physical position of the combiner (on a far side from the user). A front windshield of an automobile and the like may be used as the combiner. A different transmissive reflection member may be used as the combiner.
To improve the viewability of the information displayed by the head-up display, distortion of the virtual image needs to be reduced. The virtual image is generated from an intermediate image formed by an image forming unit. There is known a head-up display in which a free-form surface lens is arranged in the preceding stage of the image forming unit to correct distortion caused by the image forming unit (for example, see Japanese Patent No. 5370427).
The head-up display is arranged in front of the user (driver) of the moving body. If the moving body is an automobile, the head-up display is accommodated in the dashboard. What is desired of the head-up display is then to satisfy a demand for further miniaturization and improve the viewability of information.
Like the example of Japanese Patent No. 5370427, an optical system including an image forming unit for generating an intermediate image may include a correction optical element for correcting distortion and/or resolution of the intermediate image. This, however, goes against the demand for miniaturization. In addition, the need for the correction optical element results in an increase in cost.
Therefore, there is a need to provide an image display apparatus of which size and cost can be reduced while maintaining viewability (quality) of a virtual image.